Follow up on the recent post *”how can the sun just continuously burn and burn?*”
Can someone explain how the sun actually started its nuclear fission?
Oppenheimer did not go a dropped a nuke on it 😉
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One correction here: What happens in the sun is nuclear *fusion* (elements combining), not nuclear *fission* (elements splitting).
The short version: Gravity did it.
The still short, but slightly longer version:
It’s possible for nuclear fusion to happen just by the right light elements (like hydrogen) getting squeezed extremely hard. Under an absolutely incredible amount of pressure, the repulsive force between two atomic nuclei is overwhelmed, and the two nuclei combine into one, giving off more energy in the process than it took to push them together.
In a star, this pressure is provided by star’s material getting squeezed together by gravity, and the chain reaction starts when the energy each individual combination gives off makes other nuclei combine. This keeps going until eventually the star runs out of elements that can combine under those conditions because everything’s already been fused (since the repulsive force keeps increasing with each combination), at which point either the star dies quietly, or if it’s big enough it explodes in a nova or supernova (or even becomes a black hole).
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